Effect of root zone water and nitrogen regulation on cotton population physiological indices under different furrow irrigation patterns

To explore the regulation effects of water and nitrogen on cotton population growth and development under the furrow irrigation, a cotton field furrow irrigation experiment was conducted. In the experiments, three kinds of furrow irrigation patterns and three irrigation and nitrogen fertilization levels were designed. The change trends of the cotton population physiological indices were simulated using single peak Gaussian distribution model. The results showed that the model simulation accuracy was relatively high. Compared with the peak values of leaf area duration (LAD) under conventional furrow irrigations (CFI), it decreased by 39.3% under alternative furrow irrigations (AFI) and low nitrogen treatments. Under medium nitrogen treatments, there was no significant difference in all indices. Under high nitrogen treatments, the LAD peak value increased by 17.26%, while the net assimilation rate (NAR) decreased by 21.69%. Meanwhile, under fixed furrow irrigations (FFI) and different nitrogen treatments, the peak value of each indices decreased by 35.1%–44.0%. Compared with the CFI, the LAD peak value decreased by 23.94% under AFI low water treatments. LAD peak value increased by 13.63% and leaf area index (LAI) decreased by 14.2% under AFI medium water treatments. Under AFI high water treatments, there was no significant difference in all indices. Under the FFI and different irrigation treatments, each index decreased by 20.7%–47.22%. Compared with the changes of cotton biomass and yield, the changes of ground dry weight and yield were insignificant under AFI and all water and nitrogen treatments. The FFI ground dry weight decreased by 9.8%–19.3% and the cotton yield decreased by 7.6%–8.9%. The experimental results show that AFI has obvious advantage of regulation effects of water and nitrogen on the performance of cotton population and it can be used to control the population growth and development of cotton effectively. Thus, AFI is recommended in practical applications of cotton water and fertilizer managements.